New york city is the largest city in the usa. it is located on the atlantic coast in southeastern part of the state of new york. the city was founded in 1624 by the dutch colonists, and was called new amsterdam. in 1664, the british captured the city and renamed it new york in honor of the initiator of capture – the duke of york.the city consists of five boroughs: the bronx, brooklyn, queens, manhattan and staten island. the city area is 1214.9 km². the population of new york is over 8.4 million people (2013).new york, along with london and tokyo, is one of the three main centres of the world economy.there are two airports in new york – john f. kennedy international airport (jfk) and laguardia (lga).new york is a relatively young city (it is less than 400 years old), and its layout is not burdened with centuries-old layers of historical and architectural eras.skyscrapers are the basis of modern architecture in new york and are the city’s landmark (the empire state building, the chrysler building).the main attractions of new york are located in manhattan: the rockefeller center, the metropolitan museum of art, the metropolitan opera, the american museum of natural history, the un headquarters, and harlem. the statue of liberty is located about 3 km southwest of the southern tip of manhattan on liberty island.нью-йорк – крупнейший город сша. он расположен на берегу атлантического океана в юго-восточной части штата нью-йорк. город был основан в 1624 году голландскими колонистами и назывался новым . в 1664 году город захватили и переименовали его в нью-йорк в честь инициатора захвата – герцога йоркского.город состоит из пяти районов (боро): бронкс, бруклин, куинс, манхэттен и статен-айленд. площадь города – 1214,9 км². население нью-йорка более 8,4 млн человек (2013).нью-йорк, наряду с лондоном и токио, называют одним из трёх центров мировой .в нью-йорке есть два аэропорта – аэропорт им. кеннеди (jfk) и аэропорт laguardia (lga).нью-йорк – город сравнительно молодой (ему менее 400 лет), и его планировка не отягощена многовековыми наслоениями и архитектурных эпох.небоскребы составляют основу современной архитектуры нью-йорка и являются достопримечательностями города (эмпайр-стейт-билдинг, крайслер-билдинг).основные достопримечательности нью-йорка расположены в манхэттене: это рокфеллеровский центр, художественный метрополитен-музей, метрополитен-опера, американский музей естественной , штаб-квартира оон, гарлем. а примерно в 3 км на юго-запад от южной оконечности манхэттена на острове свободы находится статуя свободы.
Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long-chain molecules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other categories are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyesters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplastic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight compared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.Plastics can be classified into several broad types.1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suitable for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplastic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Examples are polythene, polystyrene andPVC.2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of thermosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.
Plastics are non-metallic, synthetic, carbon-based materials. They can be moulded, shaped, or extruded into flexible sheets, films, or fibres. Plastics are synthetic polymers. Polymers consist of long-chain molecules made of large numbers of identical small molecules (monomers). The chemical nature of a plastic is defined by the monomer (repeating unit) that makes up the chain of the polymer. Polyethene is a polyolefin; its monomer unit is ethene (formerly called ethylene). Other categories are acrylics (such as polymethylmethacrylate), styrenes (such as polystyrene), vinys (such as polyvinyl chloride (PVC)), polyesters, polyurethanes, polyamides (such as nylons), polyethers, acetals, phenolics, cellulosics, and amino resins. The molecules can be either natural — like cellulose, wax, and natural rubber — or synthetic — in polyethene and nylon. In co-polymers, more than one monomer is used.The giant molecules of which polymers consist may be linear, branched, or cross-linked, depending on the plastic. Linear and branched molecules are thermoplastic (soften when heated), whereas cross-linked molecules are thermosetting (harden when heated).Most plastics are synthesized from organic chemicals or from natural gas or coal. Plastics are light-weight compared to metals and are good electrical insulators. The best insulators now are epoxy resins and teflon. Teflon or polytetrafluoroethene (PTFE) was first made in 1938 and was produced commercially in 1950.Plastics can be classified into several broad types.1. Thermoplastics soften on heating, then harden again when cooled. Thermoplastic molecules are also coiled and because of this they are flexible and easily stretched.Typical example of thermoplastics is polystyrene. Polystyrene resins are characterized by high resistance to chemical and mechanical stresses at low temperatures and by very low absorption of water. These properties make the polystyrenes especially suitable for radio-frequency insulation and for parts used at low temperatures in refrigerators and in airplanes. PET (polyethene terephthalate) is a transparent thermoplastic used for soft-drinks bottles. Thermoplastics are also viscoelastic, that is, they flow (creep) under stress. Examples are polythene, polystyrene andPVC.2. Thermosetting plastics (thermosets) do not soften when heated, and with strong heating they decompose. In most thermosets final cross-linking, which fixes the molecules, takes place after the plastic has already been formed.Thermosetting plastics have a higher density than thermoplastics. They are less flexible, more difficult to stretch, and are less subjected to creep. Examples of thermosetting plastics include urea-formaldehyde or polyurethane and epoxy resins, most polyesters, and phenolic polymers such as phenol-formaldehyde resin.3. Elastomers are similar to thermoplastics but have sufficient cross-linking between molecules to prevent stretching and creep.
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